When a valve core of a conventional hydraulic control main valve is switched to the R position during the use of the hydraulic control main valve, a piston of the hydraulic control main valve will move downward at acceleration under the gravity action of the mechanism and the material on the piston. On the one hand, the oil fluid in the piston chamber will be discharged rapidly; and on the other hand, when the piston is moving downward at acceleration, the flow to the non-rod chamber cannot be satisfied in time, so the piston falls in a unrestricted way and insufficient oil is fed into the rod chamber of the oil cylinder to cause a vacuum, which are unfavorable.